With development of network technologies, a client imposes a higher requirement on reliability and stability of Interior Gateway Protocol (IGP). The IGP protocol includes the Open Shortest Path First (OSPF) protocol and the Intermediate System to Intermediate System (IS-IS) protocol. In the OSPF protocol, neighbor information is sent to each node in an entire network by using a link-state advertisement (LSA), so that each node performs route calculation. In the IS-IS protocol, neighbor information is sent to each node in an entire network by using a link state PDU (LSP), so that each node performs route calculation. For ease of description, information such as the LSA and the LSP is collectively referred to as a routing information update packet. In a routing system, a routing information update packet generated by each node is flooded in the entire network, thereby affecting each node in the entire network. In addition, after receiving a routing information update packet, each node updates routing information based on the routing information update packet.
Currently, the OSPF/IS-IS protocol does not provide enough information about a source router generating a routing information update packet, and when route flapping occurs, a long time is required to determine a failure source. For example, a router supporting the IS-IS protocol is used as an example. The IS-IS protocol is a link-state routing protocol, and advertisement of a route in the entire network is implemented by using an LSP packet. After receiving a flooded LSP packet, each router needs to perform verification and detection. For an LSP packet in which an error is detected during verification, the router deletes a route to a source router of the LSP packet, generates a purge LSP packet, and floods the purge LSP packet in the entire network. The purge LSP packet is used to notify another router in the entire network that the source router of the LSP packet in which an error is detected during verification is abnormal, and the route is unreachable. After receiving the purge LSP packet, the another router performs an operation the same as that performed by the foregoing router. Consequently, route flapping occurs.
If a router is faulty or is attacked by a hacker, many purge LSP packets may be generated and flooded in an entire network, resulting in route flapping. If route flapping occurs, a router generating the purge LSP packets cannot be located, and therefore a failure source cannot be quickly located.